Numerous devices, usually referred to as spirometers, have been developed to measure and monitor the breathing flow rates in human subjects. Conventional spirometers are typically used in conjunction with a breathing tube through which the inspired and expired airflows travel, and which is preferably disposable in order to minimize the risks of cross-contamination. A variety of active elements such as turbines, calibrated orifices, pitot tubes, venturis and resistive membranes are typically placed in the spirometer breathing tube in order to enable the measurement of the flow rate of the air travelling therethrough.